allow peers to be removed and cleared

This depends on zeromq 3.2+ and ffi-rzmq > 0.9.7.
use a uuid as id, for now
add Configuration and Configurable

Configuration is your average extended Hash, but it also publishes
config changes to celluloid notifications.

Configurable adds a Configuration to a class (and its instances) or
module.
add Configuration::Notifications

Makes it easier for classes to subscribe to notifications from
Configuration objects.
add RemoteNotifier subclass of PubsubNotifier

RemoteNotifier configures itself based on publishes from the
Zensu.config object. This allows live config updates.